Help with M81/82

[Nova2000]

Hi

Do you'll feel that these galaxies will be visible from my town where the naked eye limited maganitude is 4.?

My scope is a Gso 8 f6 dobsonian. 

I've seen the ring which is 9mag with a 25yr old f10 8inch reflector. 

What do you'll feel!? 

[michael.h.f.wilkinson]

Near zenith should be possible, I feel. Note however that the Ring has a higher surface brightness than M81 and M82 (although they are pretty good for galaxies). Itegrated brightness (which is the magnitude listed) is essentially how bright objects would appear if all the light was concentrated into a single point source. This would make you think that M101 (mag 7.86) was easier than the Ring (mag 8.8) or  M82 (mag 8.4), but quite the reverse is true. M101 is very difficult in light polluted skies (but quite easy under good conditions).

[Nova2000]

1 hour ago, michael.h.f.wilkinson said:

Near zenith should be possible, I feel. Note however that the Ring has a higher surface brightness than M81 and M82 (although they are pretty good for galaxies). Itegrated brightness (which is the magnitude listed) is essentially how bright objects would appear if all the light was concentrated into a single point source. This would make you think that M101 (mag 7.86) was easier than the Ring (mag 8.8) or  M82 (mag 8.4), but quite the reverse is true. M101 is very difficult in light polluted skies (but quite easy under good conditions).

Hi

So magnitude is basically how bright the object would look if all the light was concentrated in a single point? 

 

[michael.h.f.wilkinson]

Just now, Nova2000 said:

Hi

So magnitude is basically how bright the object would look if all the light was concentrated in a single point? 

 

Indeed.  Much more important from our perspective is the surface brightness, which, given the brightness of the sky background, will tell much more about how much contrast there will be between object and background.

[billyharris72]

Hi Nova. I'm pretty sure if you can see mag 4 you should be able to pick these up without too much difficulty. When I was living in Bedford I reckon I could see down to abput 3.8 or so (maybe 4, but never actually confirmed a naked eye sighting of a star at that magnitude). At new moon, on a decent night, both were relatively straightforward in my Bresser 8 inch f6 dob. Certainly enough to clearly see both and record a bit of detail (overall shape, not much more). The difficulty I had was more in finding them, since they were very far from being visible in the finder, so a bit of star hopping was required.

I'd definitely recommend, as Michael suggested, waiting till they are reasonably high in the sky (near zenith, but perferably just a little bit off as a Dob is tricky to use when it's pointing straight up). That will maximise your chances and get you the best views. Once you've seen them the first time they will be much easier to pick out in future.

Best of luck.

Billy.

[Nova2000]

7 minutes ago, billyharris72 said:

Hi Nova. I'm pretty sure if you can see mag 4 you should be able to pick these up without too much difficulty. When I was living in Bedford I reckon I could see down to abput 3.8 or so (maybe 4, but never actually confirmed a naked eye sighting of a star at that magnitude). At new moon, on a decent night, both were relatively straightforward in my Bresser 8 inch f6 dob. Certainly enough to clearly see both and record a bit of detail (overall shape, not much more). The difficulty I had was more in finding them, since they were very far from being visible in the finder, so a bit of star hopping was required.

I'd definitely recommend, as Michael suggested, waiting till they are reasonably high in the sky (near zenith, but perferably just a little bit off as a Dob is tricky to use when it's pointing straight up). That will maximise your chances and get you the best views. Once you've seen them the first time they will be much easier to pick out in future.

Best of luck.

Billy.

I better skip them from the city then. They will never get higher than 35degrees from my location. But seeing the pair from a dark site was really great. 

Thanks for the advice!! 

Clear skies 

[billyharris72]

9 hours ago, Nova2000 said:

I better skip them from the city then.

No way! I forgot that due to location they will always be in the sky for you. They will not be so well placed, but that is no reason not to try. There's only one way to find out for sure.

Billy.

[rockystar]

try them anyway, I can see them in my 8" in very light polluted skies, never taken a reading, but I'd say less than 4.2

[The Warthog]

I think you should be able to see them, especially with the Plough being so high at present. They are easy to find in a decent sky, and I find them a delight to look at. I can't see them at all in my city skies, with a limiting magnitude of about 2, at least not in my 6" reflector.

[bingevader]

On a Dobsonian mount, I always find them a bit easier to find when they're not so close to the zenith anyway!

Best of luck, let us know how you get on.